The present invention relates to thrust vectoring techniques, and more particularly, but not exclusively, relates to techniques to control thrust vectoring and nozzle throat area with variable pitch guide vanes.
With the advent of Vertical or Short Take-Off and Vertical Landing (V/STOVL) aircraft, a need has arisen for uninterrupted vectoring of thrust generated by the discharge of working fluid. One way to provide such thrust vectoring is with a cascade of individually pivotable vanes that selectably divert the working fluid as it is discharged from a nozzle. The hot gasses exhausted from a gas turbine engine are one source of working fluid which may be vectored in this manner. Alternatively or additionally, a lift fan that is driven indirectly by a coupling to a gas turbine engine may be utilized to provide a xe2x80x9ccold flowxe2x80x9d working fluid source. U.S. Pat. No. 5,209,428 to Bevilaqua et al. is cited as a source of further information concerning this type of lift fan.
For the V/STOVL mode of aircraft operation, a continuous vectoring of thrust is required throughout a wide angular range to provide lift for the aircraft. Also, a smooth transition to a horizontal cruise mode is often required. Moreover, as with most aircraft equipment, thrust vectoring systems generally must be lightweight, reliable, and compact, occupying as little space as possible. U.S. Pat. No. 5,769,317 to Sokhey et al.; U.S. Pat. No. 5,485,958 to Nightingale; U.S. Pat. No. 4,798,328 to Thayer et al.; U.S. Pat. No. 3,640,469 to Hayes et al.; U.S. Pat. No. 3,397,852 to Katzen; U.S. Pat. No. 3,179,353 to Peterson; and U.S. Pat. No. 2,989,269 to Le Bel illustrate various arrangements for vectoring thrust.
One typical drawback of these systems is the inability to selectively adjust the exit area presented to working fluid as it passes through the vanes while simultaneously and independently deflecting the exiting working fluid to vector thrust. The ability to select the working fluid exit area or throat area generally improves vectoring system efficiency. In particular, for vane cascades, it is often desirable that the collective exhaust gas flow area through the vanes be held nearly constant in order to avoid inducing instability in the operation of the gas turbine engine. For cascade vanes pivoting in unison to vector thrust, it will be appreciated that the nozzle outlet area measured normal to the flow of gas from the vectoring cascade will be a function of the sine of the vane angle. Thus, the throat area defined by cascade vanes positioned at a 45 degree angle with respect to the nominal gas flow direction will be approximately 70% of the throat area defined by the vanes when oriented parallel to the nominal gas flow. This nearly 30% difference in throat area can result in performance variations that may be difficult to reliably counteract during V/STOVL maneuvering.
One approach to this problem is to simultaneously adjust vectoring and throat area by using an independently controllable actuator for each vane in the cascade. Unfortunately, this approach is often impractical because of the attendant increase in weight, complexity, and space required for the separate actuators. Thus, needs remain for further advancements in thrust vectoring technologyxe2x80x94especially in the area of multiple vane vectoring techniques.
One form of the present invention is a unique thrust vectoring system. Other forms include unique systems and methods to position a number of vanes with a rotary drive mechanism to vector thrust.
Another form includes an aircraft defining an outlet for discharging a working fluid to produce thrust and a number of vanes pivotably coupled across this outlet to vector the thrust. Also included is a rod rotatable to pivot the vanes in accordance with threading defined along the rod.
Still another form includes a thrust vectoring mechanism with a number of vanes and a threaded rod. The rod is coupled to a vane control member that engages one of the vanes in a camming relationship. Alternatively or additionally, the rod may engage teeth of a drive member connected to another of the vanes.
Yet another form of the present invention includes an aircraft with a thrust vector mechanism that includes a number of vanes and a rod. Also included are a corresponding number of vane control members that each engage a different portion of the rod. This engagement is provided by threading, teeth, or both. The vane connection members move in response to rotation of the rod and correspondingly pivot each of the vanes.
In a further form, a unique thrust vectoring nozzle includes a number of vanes and a rod interconnecting the vanes. The vanes pivot in unison in a common rotational direction (i.e., clockwise or counter-clockwise) in response to rotation of the rod. For this form, the pivoting of each vane is scheduled to control nozzle throat area. For example, this throat area control may reduce variation in the nozzle""s discharge coefficient with changes in vane orientation, and correspondingly reduce attendant changes in effective throat area of the nozzle.
Further embodiments, objects, advantages, features, benefits, forms, and aspects of the present invention will become apparent from the drawings and description provided herein.